Electromagnetic device



Aug. 24, 1943.

H. G. BLOSSER ET AL ELECTROMAGNETIC DEVICE 1942 3 Sheets-Sheet 1 Filed May 26 [/VVE/VIOEJ Ae mazz 62 former and H0601 [amwzuon Aug. 24, 1943. H. G. BLOSSER ET AL ELECTROMAGNETIC DEVICE Filed May 26, 1942 3 Sheets-Sheet 2 laan zzmzz I g- 1943. H. G. BLOSSER ET AL ELECTROMAGNETIC DEVICE 3 Sheets-Sheet 3 Filed May 26, 1942 x k 1.1 g-7W i WW M 2% M m? 0 Z W. M z 2 m Z M mww 7 w n Q C Q Q wxmwv NM. kn, M

Patented Aug. 24, 1943 EILHCTRDMAGNETIC' DEVICE Herman G. Blosser, Pittsburgh, and Robert M. Laurensomkosedale Heights, Pa., assignors to The Union Switch & Signal Company, Swissvale; Pa, a corporation of Pennsylvania Application May 26,1942, SerialNo. 444,512

7 Claims.

Our invention relates toelectromagnetic devicesgand particularlyito' devices provided with contacts' operated by a" vibrating.- element for periodicallyiinterrupting 'orpole changing. the supply :of-direct current tothe primary. of a transformer to producealternatingcurrent in the secondary thereof.

One object of our invention is to provide a device oi the type described which may be driven from a pilot source of alternating current, and which-will accurately followthe frequency of the pilot source irrespective of Changes in the massor: resilient characteristics of: the vibrating ele-- ment-caused by wear in the contacts and irrespecti-ve of changes in the magnitude of theenergizing current.

another object orourinvention is to provide a highly eflic ient device of the type described which i capable Qfbperating a relativelylar'ge number of pole changing contacts each capable of carrying.

relatively large currents.

A still further objectiof our invention is to provide a deivce' of the type described which when energized-will startwithout appreciable delay,

and which has fan" exceptionally long life.

According to'our invention, the device" comprises a contact carrying'vibrating reed'armature"rig'idly anchored atoneend toa fixed support; and cooperating at its free end with 'two pair'sof longitudinallyspaced poles which togetherwith the'armature comprise part'of a motorelement for causing the "armature to vibrate. The poles of each pair are connected with the corresponding poles ofthe other pair bybackstraps; and are each provided with bifurcated p'ele' faces the'biiurcations of each of which are laterally spaced apart adistancewhich is sufli cientto-permit' the armatureto-swing into the space formedbetween them. The bifurcations ofthe two pole pieces'nearest the free end ofthe armature are disposed' in spaced confronting relation'so that airga-ps are formedbetweenthem,

butth'e bifurcations of the other pair are-disposed with-their confron'ting ends touching so that th'eyform a low reluctance magnetic path to and frornthe-armature; andalso around the armature; without interfering with its move-' ment. The two backstraps are bridged by a permanent magnet which polarizes the two pole pieces nearest the free end of the armature. Shunting of the flux from this magnet through the other pair of pole pieces is prevented by nonmagnetic bushings interposed between these pole pieces and the associated backstraps. The energizing winding of the device surrounds the armatime between the two pairs of pole pieces, and due to the polarizing effect of the permanent magnet the reed armature swings at its free end toward one pole piece or the other depending upon the polarity of the current supplied to this winding. The reed armature and associated contacts are so designed that the resulting assembly has a natural period of vibration which is slightly higher than the frequency at which it is desired to have the armature vibrate, whereby when the energizing winding is supplied with current of the frequency at which it is desired to have the armature vib'rate the armature will vibrate at this frequency irrespective of changes in its mass and resilient characteristics caused by contact wear.

Other objects and characteristic features of our invention will become apparent as the description proceeds.

We shall describe one form of device embodying our invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a vertical sectional view showing one form of device embodying our invention. Fig. 2 is a right-hand side View of the device shown in Fig. 1. Fig. 3 is a detail sectional view of a portion of the relay taken at right angles to Fig, 1. Figs. 4 and 5 are detail sectional views taken on the lines IV-IV and VV, respectively, of Fig. 1.

Similar reference characters refer to similar parts in each of the several views.

Referring to the drawings, the device in the form here illustrated comprises a suitable case consisting of a top plate I of insulating material secured tothe upper end of a substantially U- shaped nonmagnetic bracket 2, a metallic base plate 3 secured to the lower end of the bracket 2, and a transparent glass cylinder 4 clamped between the top plate I and the base plate 3. A gasket 5 of cork or other suitable material is interposed between the top plate I and the upper end of the cylinder 4, and a similar gasket 6 is interposed between the bottom plate and the lower end of the cylinder, thereby sealing the case against the entry of dust or other foreign substances.

A- vertically disposed vibrating reed armature 1 (see Fig 3) of suitable magnetizable material is suspended from a bracket 3 secured to the underside of the top plate, and this armature cooperates at its lower end with upper and lower pairs of pole pieces a, iii, and ii, [2, respectively, which polepieces together with the armature comprise part of a motor element, for causing the armature to vibrate. The armature is relatively stifi, and in order to cause it to'vibrate' in the desired manner it is essential that the upper end of the armature be rigidly fixed against movement. To this end, the armature is fastened as by riveting to the bracket 8, and is also securely clamped againstcne side of a depending portion 8a of the bracket 8 by means of a clamping block 13 and clamping bolts Hi. Moreover, the bracket 8 is disposed in a' groove 15 formed in the underside of the top plat,e,'and is securely fastened to the top plate by means of two machine screws 16 and two terminal posts ing relation but are spaced apart by air gaps of sumcient lengths so that the armature will not.

swing between the bifucations on either pole piece until it has moved away from its mid stroke position an appreciable distance. The other pole pieces 9 and It are so adjusted that the ends of their bifurcations are also in confronting relation but these ends, instead of being'spaced apart, are in actual contact as shown in Fig. 4

so that they form a low reluctance magnetic path around the armature from one pole piece to the I 1 other without interfering with its movement, and

also from the armature to either pole piece in any position of the armature.

The motor element furtherincludes a pair of permanent magnets and 25, and an energizing winding 21. The permanent magnets bridge the bars 26 and 2! directly opposite the lower pair of pole pieces H and I2, and serve to polari'i. The terminal posts ii are in the form of studs, the lower ends of which are screwedinto tapped holes provided in the bracket, and the upper ends of which project above the top plate and carry the usual clamping nuts l3 for securing circuit wires to the terminal posts. vIt will be.

apparent that the terminal posts are electrically connected through the mediumof the bracket with the armature l, and. these terminal posts provide a convenient means for establishing eX- ternal electrical contact with the armature for a purpose whichcwill appear presently,

.The motor element includes in addition to the pole pieces two vertically disposed bars 2% and' 21 which are secured, respectively, to the legs 2a and 2b of the bracket 2 by means of machine. screws 5| which pass through clearance holes in the bars and are screwed into tapped holes formed 'in inwardly projecting lugs 20 and 2d provided on'the legs 2a and 21). These bars, which are of magnetizable material, are provided at their upper ends with split portions 29a and 2 la terminating in alignedcircular openings 26?) and Eli), and at their lower ends with other split portions 280 and 2 lo terminating in aligned cir- I cular openings 26d and Zld. The upper openings 20?) and Eib receive with a snug fit split non-magnetic bushings 221and 23,=which bushings, in turn, receive the rounded outer ends of the, pole piecesa and it, while the lower openings 23d and Zid receive with a snug'fit the rounded outer ends of the lower polepieces ii;

and i2. Each split portion is provided with an associated clamping screw 2% which; when tightened, draws the two halves of the split portion together and thereby clamps the pole pieces securely in a fixed position with respect to the associated bar It will be obvious that the bar 28- serves as a backstrap to magnetically connect the-two pole pieces 9 and ii together, and that I the bar 2 i1 similarly serves as a backstrap to magneticallyconnect the two pole pieces ill and 12' I together, but that, due to the non-magnetic bushings 22 and 23, a relatively high reluctance path is provided between the pole pieces 9 and iii and the associated bars.

' are secured in place by brackets 29 and 3H and ize these pole pieces. shunting of the flux from these magnets through the other pair of pole pieces is prevented for the most part by the nonmagnetic gaps provided betweenthe pole pieces 9 and i9 and bars 2fland 2! by the bushings 22 and 23 described hereinbefore. The magnets bolts 3 l The energizing windihg'Z? is wound on a hollow spool 32 which surrounds the armature with considerable clearance between the two pairs of pole pieces. This spool rests on the pole pieces of the lower pair, and is maintained in the desired lateral position by means of notches 32a in the upperspo'ol head, which notches receive the bars 29 and 2!; 'Vertical movement of the spool 32 is prevented by spring clips 33 interposed between the upper-spool head and the upper pole pieces 9 and H3. The windingZ'i is provided with 1 leads 21a secured to terminal posts 3M mounted on the top plate I. a

The armature carries" a' contact assembly comprising a plurality of flexible contact fingers 3d and 35, each of which cooperates with a fixed contact member 3 1a or 3540 to close a contact M-Sd or.35 3 5a according as the armature is swung in one direction or the other from the position shown} The contact fingers aredisposed in pairs and are secured at their upper ends by means of studs 36 to conducting brackets 37.

The brackets 31 extend transversely to the armature,l an'diare secured intermediate their ends to r the armature at a point well below they point of maximum stress in order to minimize the'chance of breakage of the armature. Interposed between the brackets and the fingers are conducting strips 38 which receive the fingers and serve to maintain the fingers in the desired vertical positions, and disposed on thestuds between the I brackets are spacing blocks 39 which add to the rigidity of the contact assembly. The positions of theflexible fingers when the fingers are out of engagement with the associated fixed contact members aredetermined by stops 50 which areclarnped against the outer faces of the fingers by means of the associated studs 35, and each of which stops isprovided at its lower end with an opening through which a low resistance contact button carried; by the associated finger projects. Thestops are so adjusted byjbending them that the fingers will break the contacts in the desired positions when the armature is oscillating. It will be apparent that the fingers 3d and 35 are each electricallyconnected through the. medium of the blocks 38,- studs 36 and brackets?! with the armature Hand since; as was pointedout hereinbefore, the armature 1 is electrically" connected with the-terminal posts H; it follows that the terminal posts l1 provide aconvenientmeans for obtaining external electricalcontact withthecontact fingers 34' and- 35;

The fixed contact members 34a and 35'a'are similar to the fixed contact membersla'a and l8b described and claimed in an application for Letters Patent of" the United States; Serial No. 304,811, filed by Herman G, Blosser on Novemher-16, l939;-for-Electrical relays; which application became Patent No: 2,285;890 on June 9; 1942; and are adjustably secured to the lower endsof terminal posts 45' mounted on the top plate I in amanner which is; also described in thesaid Blosser'application. It is believed to be unnecessary; therefore; to'describe the constructionand-'- arrangement ofthese fixed contact membersany-further herein; y

In operation; the winding 27 i supplied with" alternating current of'the frequency at Whichit is desired to havethe armature 1 vibrate; anddue to the polarizing effectv of the permanent magnets the lower end of the armature moves toward the pole piece llor th pole piece l2 epending upon the instantaneous polarity of the alternating current in thewinding'zl atanyone time.- In other words; the armature is poled in onedirection forthe positive half of'the alternating current cycleand in the opposite direction for the negative half of the alternating current cycle,- and since the-pole pieces II and I! are, always poled in thesamedirection due to the permanent magnet flux, an alternating'force is 3 producedinthe lower end' of thearmaturewhich oauses-thearmature to oscillate: As is Well'understood; the power required tocause the'arma ture tooscillate will be a minimum Whenl the armature and associated contact assembly are mechanically tuned-to oscillate at the same frequency as thefrequency of the alternating'current which is supplied to winding 21. We have. found, however, that if the vibrating part are tuned to' resonance at the exact frequency at which it is desired to have thearmature oscillate; the change in mass and resilient characteri'stics of the vibrating parts caused by contact wear will cause the amplitudeqof vibration of: thearmature to change, and-as a result; if sufficientwear takes place the armature. will stall This is undesirable and in accordance with our invention we avoid this change in amplitude by so proportioning the vibrating parts that they have'a resonant frequency which is slightly higher; for example 8 per cent higher; than the frequency of'the energizing current. 'This insures that the armature will always be in the mid position-whenvthe maximum force is applied" to the;

nerdescribed, the driving forceapplied to:the,- armature. in. either. direction is" out off as soon' as the armature moves between the bifurcations: This construction materially assistsin maintain-- ing the armature amplitude constantiirrespective of changes in the magnitude of the-applied.

alternating. current.

It should-also be particularly pointed out that since the upper pole pieces are bifurcated and are disposed with the confronting ends of the use for supplying alternating current from a scurceof direct current in certain forms of railway signaling systems where no commercial source of'alternating current of the desired frequency isavailable, or if a commercial source of alternating current of'the desired frequency is available, then as a standby source to maintain the signaling system in operation in the event of an interruption in the commercial source. When used ior either purpose, a pilot source of alterhating current for operating the device may be readily obtained through the medium of a vibratoriwhich, due to the small amount of power requiredto drive the device, can be inexpensive, and-which will accurately maintain its frequency for a long" period of time. Since the device operates at the frequency Of'the pilot source, the frequency ofithe current generated by the device is unaffected by contact wear, and the resulting combination'hasa very long life.

Although we; have herein shown and described only one form of electromagnetic device embodyil'lg. our invention, it is understood that various changes .and modifications may be made therein within the scope of the appended claims Without departing from the spirit and scope of our in-- vention.

Having thus described our'invention, what We claim-is:

1-. Anelectromagnetic device comprising 3, vibrating reedarmature-anchored at one end and cooperating at its free endwi'th apair ofpole piecirs-having bifurcated'pole faces disposed with their bi-furcaticns in spaced confronting relation, the bifurcations on each said pole piece being far enough apart to permit said armature to swing intothe space between them, other pole-means surrounding said armature with clearance intermediate its ends and providing a low reluctance path fromsaid armature to said pole means, nzagnetizable means providing a relatively high reluctance pathfrom the pole pieces of said pair ofpole pieces to said pole means, means for polarizing said pole pieces, andmeans for produc ing. a flux in said armature which reacts with the. polarized flux supplied to said pole pieces to. cause said armature to oscillate.

An. electromagnetic device comprising a vibrating reed. armature anchored at one end and cooperating at its-free end with a pair of pole pieces having bifurcated pole faces disposed: with their bifurcations in spaced confronting:

relation, the bifurcations on each said-pole piece being far enoughapart to permit said armature to swing-intothespace between them; other pole meanssurrounding said armature with clearance intermediate its ends and providing a low re'-' luctance pathirom said armature to said pole means; magnetizable means providing a relatively high reluctance path from the pole pieces of said pair of pole pieces to said pole means,

bifurcations in" actual contact, these pole pieces for producing an alternating flux of a particular frequency in said armature, the parts being so proportioned that said armature is resonant at a frequency slightly higher than the frequency of said alternating flux.

3. An electromagnetic device comprising a vibrating reed armatureanchored at one end and cooperating at its free end with a pair of pole pieces having bifurcated pole faces disposed with their bifurcations in spaced confrontlng relation, the bifurcations on each said pole piece being far enough apart to permit said armature to swing into the space between them, other pole means surrounding said armature with clearance intermediate its ends and providing a low reluctance path'from said armature to said pole means, magnetizable means providing a relatively high reluctance path from the pole pieces of said pair of pole pieces to said pole means, means for polarizing said pole pieces, and a winding surrounding said armature between said pole pieces and said pole means, the parts being so proportioned that when said winding is supplied with alternating current :of a particular fre quency said armature will oscillate. v

4. An electromagnetic device comprising a vibrating reed armature anchored at one end and cooperating at its freeend with two spaced pairsrof pole pieces, said pole pieces being formed with bifurcated pole faces the bifurcations of which are far enough apart to permit said armature'to freely enter the space between them, the two pole pieces of the pair nearest the free end of said armature being disposed with their bifurcations in spaced confronting relation and the pole pieces of the other pair being disposed with their bifurcations touching to provide a low reluctance magnetic path from one pole piece torthe' other past said armature and from said armature to both said pole pieces, magnetizable members connecting the corresponding pole pieces of the two pairs of pole pieces together, means for polarizing the pole pieces nearest the free end of said armature, means for providing.

a relatively high reluctance path'for said polarizing flux; from said members to the pole pieces of the other pair, and means for producing a flux in said armature to cause said armature to oscillate I 5. An electromagnetic device comprising a vibrating reed armature rigidly anchored at one end and cooperating at its free end with two spaced pairs of pole pieces, said pole pieces being formed with bifurcated pole faces the bifurcaarmature to oscillate,- a contact assembly securedto said armatureand including aplurality of,

flexible contactfingers, and a fixed contact cooperating with each finger, said armature and contact assembly being so proportioned that they have a resonant frequency slightly higher than the frequency at which said armature is caused pole piece to the other past said armature and to oscillate to provide constancy of armature amplitude irrespective of contact wear. r 6. An electromagnetic devicev comprising a vibrating reed armature rigidly anchored at one end and cooperatingat its free end with two spaced pairs of pole pieces, said pole pieces being formed with bifurcatedpole faces the bifurcations of which are far enough apart to permit said armature to freely enter the space between them, the two pole pieces of the pair nearest the free end of said armature being disposed with their bifurcations in spaced confronting relation and the pole pieces of the other pair being dis posed with their bifurcations touching to provide a low reluctance magneticipath from one from said armature to both said pole pieces,

tions of which are far enough apart to permit said armature to freely enter the space between them, the two pole pieces of the pair nearest the free end of said armature being disposed with their bifurcations in spaced confronting pieces together, means for polarizing the pole pieces nearest the free end of said armature, means for providing a relatively high reluctance path for said polarizing flux from said members to the pole pieces of the other pair, means for producing a flux in said armatureto cause said magnetizable members connecting the corresponding pole pieces of the twopairs of pole pieces together, means for polarizing the pole pieces nearest the free end of said armature, means for providing a relatively high reluctance path for said polarizing flux from'said members to the pole pieces of the other pair, and means for producing an alternating flux in said armature having a frequency slightly below its natural resonant frequency to cause said-armature to oscillate at the frequency of said flux.

'7. An electromagnetic device comprising a vibrating reed armature rigidly-anchored at one end and cooperating at its free end with two spaced pairs of pole pieces, said pole pieces being formed with bifurcated pole faces thebifurcations of which are far enough apart to permit said armature to freely enter the space between them, the two .pole pieces of the pair nearest the free end of said armature being disposed with their bifurcations in spaced confronting.

relation and the pole pieces of the other pair being disposed with their bifurcations touching and from said. armature to both said pole pieces,

magnetizable. members connecting the corresponding pole pieces of the two pairs of pole pieces together, means for polarizing the, pole pieces nearest the free end of 'saidarmature, means for providing a relatively high reluctance path for said polarizing flux from said members to the pole pieces of the other pair, a. winding surrounding said armature between said pairs of 'pole pieces for producing an alternating flux of V a particular frequency in said armature, a'contact assembly including a plurality of pairs of flexible contact fingers secured to said armature,

and fixed contacts cooperating withsaid con-' tact fingers, said armature and contact assembly being proportioned to have a resonant frequency of vibration slightly higher than the frequency of said flux; whereby the amplitude of vibration of said armature will remain substantially constant irrespective of contact wear or changes in resiliency of the vibrating parts caused thereby, r

I-ERMAN G. BLOSSER.

- ROBERT 'M. LAURENSON. 

